Category Archives: Magnet Design

Magnets for Small-Scale and Portable NMR

Blümich, Bernhard, Christian Rehorn, and Wasif Zia. “Magnets for Small-Scale and Portable NMR.” In Micro and Nano Scale NMR, by Jens Anders and Jan G. Korvink, 1–20. Advanced Micro and Nanosystems. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2018.

Nuclear magnetic resonance (NMR) exploits the resonance of the precessing motion of nuclear magnetization in magnetic fields. From the measurement methodology, three groups of common techniques of probing resonance can be assigned: those employing forced oscillations, free oscillations, and interferometric principles. In either case, the sensitivity depends on the strength of the nuclear magnetic polarization, which, in thermodynamic equilibrium at temperatures higher than few degrees above absolute zero, is in good approximation proportional to the strength of the magnetic field. In recognition of this fact, one guideline in the development of NMR magnets has always been to reach high field strength.The highest field strength of temporally stable magnetic fields today is achieved with superconducting electromagnets. This is why most standard NMR instruments used for NMR spectroscopy in chemical analysis and magnetic resonance imaging (MRI) in medical diagnostics employ superconducting magnets cooled to the low temperature of boiling helium with cryogenic technology.

Low-cost, pseudo-Halbach dipole magnets for NMR

Tayler, M.C. and D. Sakellariou, Low-cost, pseudo-Halbach dipole magnets for NMR. J Magn Reson, 2017. 277: p. 143-148.

We present designs for compact, inexpensive and strong dipole permanent magnets aimed primarily at magnetic resonance applications where prepolarization and detection occur at different locations. Low-homogeneity magnets with a 7.5mm bore size and field up to nearly 2T are constructed using low-cost starting materials, standard workshop tools and only few hours of labor – an achievable project for a student or postdoc with spare time. As an application example we show how our magnet was used to polarize the nuclear spins in approximately 1mL of pure [13C]-methanol prior to detection of its high-resolution NMR spectrum at zero field (measurement field below 10-10T), where signals appear at multiples of the carbon-hydrogen spin-spin coupling frequency 1JCH=140.7(1)Hz.

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